<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<title>hello world</title>
<head>
    <!-- css 表现标准语言，定义页面样式-->
    <style type="text/css">
        body{
            background-color: darkgrey;
        }
    </style>
</head>
<body>
<h1>hello world</h1>
</body>
<html>